This invention relates generally to the testing of electronic devices, such as packaged integrated circuits (ICs) which are mounted on device under test (DUT) boards, and more particularly the invention relates to a tool for handling DUT boards undergoing electrical testing.
Integrated circuits are typically tested in computer controlled test equipment in order to identify any defective circuits. The integrated circuits are packaged such as in dual in-line packages (DIPs) which can be plugged into sockets on a printed circuit board (PCB) for testing. The PCB will typically have a plurality of sockets for packaged ICs. Metal traces on the PCB connect the sockets to an edge connector on the PCB which is plugged into the test equipment.
A serious problem in handling ICs arises from the buildup of static electrical charge in the test environment. The electrostatic charge generally builds up over materials and components due to friction, movement, electrical currents, and other factors. Once such charge is created, it will discharge through any available path to ground or other electrical potential. An uncontrolled and sudden discharge can inadvertently destroy or degrade sensitive electronic devices, such as ICs. In test equipment, such discharge may take place through the user, cables, equipment cabinet frames, and the like.
Thus, it is critical that the devices being tested are not damaged by ESD either before, during, or after testing. Any such damage may ruin the device or may invalidate any collected test data.
Normally, the DUT boards are loaded with test devices over a table away from the test system. Once the DUT boards are loaded with test devices, they are carried over to and are connected with the test system. After the test is completed, the DUT boards are moved from the test system and returned to the loading table. The devices are then removed from the DUT board and stored in anti-static tubes.
Even if all normal precautions are taken, such as having the test operator use a ground strap, anti-ESD mats around the table and the like, there are still potential situations where the test device remains unprotected. Electrical charge can build up while the test device is inserted into the board test socket, and charge can also build up while transporting the DUT board from the table to the system, especially if the test operator has to disconnect a ground strap to reach the test system. Additionally, charge can build up while the DUT board is inserted or plugged into the test system and again when the DUT board is removed from the test system.
The only method of fully protecting a device against any type of ESD damage is to have all pins of a test device physically shorted to each other. This will prevent any charge buildup or electrical current flow between pins. Having an individual test device ESD tool does help protect devices most of the time while in transit, but such tools are difficult to remove and install once the board is inserted into the test system. Generally the DUT boards are located in hard to reach areas, and they are often too close to each other to allow the test operator to reach in and install or remove individual anti-ESD tools.
The present invention is directed to providing an ESD tool for handling DUT boards which overcomes these limitations in the prior art.